While the linear valley topography suggests rifting along the ridge, the velocity models do not show obvious axial symmetry.
The normal oceanic crust was identified beneath the Zenisu Ridge by a velocity structure study using OBS (Nakanishi et al. 2002), and the magnetization highs associated with the ridge topography were identified by a magnetic inversion study (Kido and Fujiwara 2004).
We began by plotting histograms of the direction of cell velocity relative to ridge alignment.
This crustal layer cools as it moves away from the ridge crest, and its seismic velocities increase correspondingly.
If the liquid front stays attached, drag from these ridges can limit the spreading velocity of the liquid.
The Oki-Daito Rise, southwest of the main ridge, is an exception in terms of velocity structure, as it has a thinner crustal section.
The maximum velocity measured for the Pilot Ridge debris flow was about half the average for other debris flows in the Sierra Nevada (DeGraff, 1994).
However, at the center of the Bonin ridge, the gravity anomaly derived from the original velocity model is ∼50 mGal lower than the observed data.
Although the origin of the thick materials is unknown, the lower Pn velocity of 7.8 km/s beneath the ridge seems to be similar to the KPR in general.
Velocity and gravity models across the ridge suggest an episode of westward underthrusting of the WPB oceanic crust beneath the Huatung Basin (Deschamps et al. 1998; Eakin et al. 2015).
